Solid-state image sensing device and manufacturing method thereof
View Patent ↗Pixel portions each of which has a charge storage portion formed in a semiconductor substrate 11 and a transfer gate for transferring charges stored in the charge storage portion are isolated from each other by a device isolation region in the semiconductor substrate. A buried gate electrically connected to the transfer gate is embedded in the device isolation region. The buried gate includes a gate dielectric film and gate electrode formed in a trench of the semiconductor substrate.
1. A solid-state image sensing device comprising:
a charge storage portion formed in a semiconductor substrate;
a floating diffusion portion formed correspondingly to the charge storage portion where the floating diffusion portion is at a location spaced from the charge storage portion in the semiconductor substrate;
a device isolation region formed in the semiconductor substrate so as to surround sides of a pixel portion including the charge storage portion and the floating diffusion portion in the semiconductor substrate;
a transfer gate formed on the pixel portion in the semiconductor substrate; and
a buried gate embedded in at least a part of the device isolation region;
wherein a first gate electrode of the buried gate is electrically connected to a second gate electrode of the transfer gate,
the second gate electrode is disposed over a region located between the charge storage portion and the floating diffusion portion of the pixel portion, and
the first gate electrode is, when viewed from the charge storage portion, formed in the device isolation region opposite to a side where the second gate electrode is disposed.
2. A solid-state image sensing device of claim 1 ,
wherein the first gate electrode is formed through a first gate dielectric film formed in a trench of the semiconductor substrate,
the second gate electrode is formed through a second gate dielectric film on the pixel portion, and
the first gate dielectric film and the second gate dielectric film are continuously formed by the same dielectric film.
3. A solid-state image sensing device of claim 1 , wherein the first gate electrode and the second gate electrode are continuously formed by the same conductive film.
4. A solid-state image sensing device of claim 1 , wherein the buried gate embedded in the device isolation region surrounds the charge storage portion.
5. A solid-state image sensing device of claim 1 , wherein the buried gate is embedded in part of the device isolation region under the transfer gate.
6. A solid-state image sensing device of claim 1 , wherein the device isolation region has a depth of ⅓ or more of a depth of the charge storage portion.
7. A solid-state image sensing device of claim 1 , wherein the charge storage portion has a depth of 0.3 μm or more from a surface of the semiconductor substrate.
8. A solid-state image sensing device of claim 1 , wherein the device isolation region has a trench structure.
9. The solid-state image sensing device of claim 1 , wherein an upper surface of the first gate electrode is lower than an upper surface of the second gate electrode.